Make palantir-java-format configuration cacheable

[kelvinou01]

Before this PR

Current working state: trying to get every test in pjf to work with --configuration-cache. PalantirJavaFormatPluginTest is failing...

- [error] cannot serialize object of type `org.gradle.api.internal.artifacts.configurations.DefaultLegacyConfiguration`, a subtype of `org.gradle.api.artifacts.Configuration`, as these are not supported with the configuration cache.
    - field `configuration` of `com.palantir.javaformat.gradle.JavaFormatExtension_Decorated`
        - bean of type `com.palantir.javaformat.gradle.JavaFormatExtension_Decorated`
            - field `__extension__` of `com.palantir.javaformat.gradle.FormatterServiceService$Params_Decorated`
                - bean of type `com.palantir.javaformat.gradle.FormatterServiceService$Params_Decorated`
                    - Gradle runtime

...which is weird. Using a build service in a task should be configuration-cache safe.

After this PR

==COMMIT_MSG==
==COMMIT_MSG==

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Description

Make palantir-java-format configuration cacheable

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